1. Field of the Invention
The present invention relates to the polymerization and hardening of dental compositions which are adhesive towards tooth and dental restorative materials such as metals, ceramics, polymers, etc. and comprising monomers containing acidic groups in the molecule thereof by irradiating the dental compositions with visible light That is, the present invention relates to dental compositions comprising monomers containing acidic groups in the molecule thereof and polymerization initiators capable of polymerizing and hardening the monomers by irradiation of visible light.
2. Discussion of the Background
In dental treatment in recent years, an important technique has been the technique for adhesion to the tooth or metals. It is vinyl monomers containing acidic groups in the molecule thereof that plays the greatest role for enhancing the adhesive property In the case of using these monomers, the adhesion to the tooth or metals sufficiently reaches a level significant for dental treatment. Examples of such monomers include methacrylic acid esters containing in the molecule thereof aciding groups such as phosphoric or phosphonic acid diester groups, phosphoric or phosphonic acid mono ester groups, pyrrophosphoric acid groups, phosphinic acid groups, carboxyl groups, acid anhydride groups, acid halide groups, etc.
In recent dental techniques, attention has been focused upon a method for photohardening technique, in place of a conventional method using redox type polymerization initiators, as a method for hardening dental compositions. For this reason, it has been attempted to incorporate photopolymerization initiators into polymerizable monomer-containing compositions, in order to apply the photohardening method. As known photohardening techniques in the prior art, a method using .alpha.-diketones, etc. as sensitizers and amines as accelerators (U.S. Pat. No. 4,071,424), a method using benzoin alkyl ethers or benzyls as sensitizers and organic peroxides as accelerators (Japanese Patent Application OPI 102/80), a method using .alpha.-diketones as sensitizers and organic peroxides as accelerators (U.S. Pat. No. 4,459,193), etc. are known.
However, in the case of applying the catalyst systems using organic peroxides or tertiary amines as accelerators to photohardening of the above-mentioned polymerizable compositions containing the acidic group-containing monomers, irradiation to light requires a longer period of time than in the case of photopolymerizing conventional polymerizable compositions containing no acidic group-containing monomers but containing (meth)acrylic acid esters, which is not practical.